Casus belli

A Casus Belli, sometimes abbreviated CB and meaning "Cause for War" in Latin, represents a justification for war that is recognized as legitimate by other characters. A ruler must have a valid Casus Belli in order to be able to declare war upon another ruler and can only gain from a war what the Casus Belli specifies.

War Target[edit]

The War Target is the map region which is targeted by a Casus Belli. If the Casus Belli does not target a map region then the defender's Realm Capital becomes the War Target.

The attacking side gains more War Score by occupying Holdings locates in the War Target region. After a grace period the defender will passively gain War Score by holding all Counties in the War Target region.

CB list[edit]

Each Casus Belli will cost Prestige and/or Piety. If a character cannot pay the cost it can pay with a Level of Prestige or Level of Devotion instead. Declaring war against a character's Head of Faith costs 500 Piety if the Head of Faith is Spiritual and 100 Piety if Head of Faith is Temporal.

Casus Belli costs can be removed via one of the game rules.

Casus Belli	Requirements	Cost	Enforce Demands effect	White Peace effect	Surrender effect
Independence War	Target is the Liege	500 Prestige if not Tribal 250 Prestige if Tribal	Attacker becomes independent	Attacker stays a vassal	Attacker stays a vassal Defender imprisons the attacker Defender gains title revocation reason
Claims	Claim on the target Rightful Ownership innovation if another character's Claim Divine Right innovation if own Claim	100 Prestige per County (own claim) 200 Prestige per Duchy (own claim) 400 Prestige per Kingdom (own claim) 800 Prestige per Empire (own claim) 250 Prestige per County (other's claim) 500 Prestige per Duchy (other's claim) 1000 Prestige per Kingdom (other's claim) 3000 Prestige per Empire (other's claim)	Claimant gains the targeted Titles Attacker gets a Weak Hook on Claimant	Defender keeps their titles	Defender keeps their titles Claimant loses the Claims used
Subjugate	One of the following Tribal government, Distinguished level of fame, and the Target has Tribal Government Eastern religion and Exalted among Men level of fame, and the Target follows an Eastern Religion Temporal Head of Faith and Devoted Servant level of devotion, and the Target shares your Faith	1000 Prestige if not Tribal 500 Prestige if Tribal	Attacker becomes the defender's liege	Defender stays independent	Defender stays independent Attacker's Factions gain Discontent
Raid for Captives	Faith has the Human Sacrifice tenet	80 if faith has the Armed Pilgrimages tenet 100 if faith hasn't the Armed Pilgrimages tenet	Attacker imprisons 3-5 of the defender's courtiers	Attacker gains no prisoners	Defender gets 3-5 prisoners if same tenet
Excommunication War	Same faith Target is independent Target has the Excommunicated trait	None	Defender suffers succession	Defender keeps their titles	Defender keeps their titles Defender loses the Excommunicated trait Attacker loses Opinion with Head of Faith
Ducal Conquest of County	Conquest lifestyle perk Attacker owns a County in the same uncreated Duchy	350 Prestige if target's title rank is Count 750 Prestige if target's title rank is above	Attacker gains the targeted County	Defender keeps their titles	Defender keeps their titles Attacker's Factions gain Discontent
Forced Vassalization	Forced Vassalage lifestyle perk Target is an independent neighbouring realm Target is not a Holy Order or Head of Faith	125 Prestige per County	Attacker becomes the defender's liege	Defender stays independent	Defender stays independent Attacker's Factions gain Discontent
Laudably Conquer County	Request Claim on Ireland decision Target is in the Hibernia region Do not have the same Liege	150 Prestige if Feudal and different faith 75 Prestige if Tribal and different faith 100 Piety if Feudal and same faith 50 Piety if Tribal and same faith	Attacker gains the defender's titles	Defender keeps their titles	Defender keeps their titles Attacker's Factions gain Discontent
Mongol Invasion of Kingdom	Mongol Empire title Established level of fame Tribal government Realms are adjacent	200 Prestige	Attacker takes all titles from Hostile/Evil faiths Attacker vassalizes all rulers of other faiths	Defender keeps their titles	Defender keeps their titles Attacker's Factions gain Discontent
Restore Imperial Province	Roman Empire title Duchy was part of the Roman Empire Religion is Christian or Greco-Roman	None	Attacker gains the targeted Duchy	Defender keeps their titles	Defender keeps their titles Attacker must pay war reparations

De Jure CBs[edit]

All Title owners have a De Jure CB towards characters who own a lower Title that belongs to the de jure territory of the higher Title. All De Jure CBs cost 100 Prestige per County in the War Target Title and have a War Contribution Share of 300 Prestige.

If the war ends by enforcing demands the attacker will gain the War Target Title and if it's a Vassal its Liege will gain a Weak Hook on them
If the war ends by white peace the defender keeps the War Target Title
If the war ends by surrender the defender's keeps the War Target Title and the attacker must pay Gold

War Target rank	Required Innovation
County	Casus Belli
Duchy	Chronicle Writing
All Titles	Rightful Ownership

Conquest CBs[edit]

The following CBs are only available to Rulers who have Clan or Tribal government or whose Faith has the Warmonger or Pursuit of Power tenets.

If the war ends by enforcing demands the attacker will gain the War Target Title and Fame equal to the War Contribution Share
If the war ends by white peace the defender keeps the War Target Title and the attacker loses 75 Prestige
If the war ends by surrender the defender's keeps the War Target Title and the attacker must pay Gold and gain +25 Faction Discontent

War Target rank	Required Level of Fame	Same Faith cost	Different Faith cost	War Contribution Share
County	Established	50 if character has Tribal government 100 if character has Clan government	75 if character has Tribal government 150 if character has Clan government	75
Duchy	Illustrious	250 if character has Tribal government 500 if character has Clan government	375 if character has Tribal government 750 if character has Clan government	150
Kingdom	Exalted Among Men	2000	2000	350

Holy War CBs[edit]

The following CBs will cause a Holy War instead of a regular one and require the Faith to be organized and to not have the Pacifism or Dharmic Pacifism tenets and can only target rulers whose Faith is considered Hostile or Evil.

If the war ends by enforcing demands the attacker will gain all Titles held by Rulers of different Faith and vassalize all Rulers of the same Faith in the War Target region. The attacker's faith loses the Fervor cost and the defender's faith gains the twice that amount.
If the war ends by white peace the defender keeps all their Titles and the attacker loses 50 Piety
If the war ends by surrender the defender's keeps all their Titles, the attacker must pay Gold and gain +25 Faction Discontent and -15 Vassal Opinion for 5 years

War Target rank	Required Level of Devotion	Fervor cost	Piety cost (without Armed Pilgrimages tenet)	Piety cost (with Armed Pilgrimages tenet)	War Contribution Share
County	Dutiful	1	100	80	100
Duchy	Faithful	2	200	160	200
Kingdom	Paragon of Virtue	5	750	600	500

Migrate to Pannonia[edit]

Migrate to Pannonia is a unique Casus Belli with special mechanics that can only be used once per game by characters of Táltosist faith who make the Prepare to Cross the Carpathians decision against characters in the Pannonian Basin region. If the Hungarian Migration game rule is set to Immediate the game will start with the casus belli being used by Grand Prince Álmos Ügyekfi of the Mogyër Confederation against King Boris of Bulgaria.

If the war ends in white peace the defender keeps his or her titles and if it ends in surrender the attacker's factions will also gain discontent. If the war ends by enforcing demands however it will have the following effects:

Attacker gains all titles held by the defender in the Pannonian Basin region
Attacker gains the Kingdom of Hungary title, which replaces Kingdom of Pannonia
Any other kingdom title held by the attacker is destroyed
Any held title that is not within the de jure realm of Kingdom of Hungary is given to another character
All vassals that are not within the de jure realm of Kingdom of Hungary become independent
All controlled counties convert to Mogyër culture and Táltosist faith
All previously controlled counties convert to Pecheneg culture

When the Casus Belli is used it will spawn the following army for as long as the attacking character lives:

Years	Levies	Horse Archers
867-889	3000	2000
890-904	5000	3000
905+	6000	4000

Varangian Adventure[edit]

Varangian Adventure is a unique Casus Belli with special mechanics that can only be used during the Tribal Era on Counties and Duchies owned by characters from a different Culture Group and costs 1000 Prestige. To be used it requires the Varangian Adventurers innovation, which is only available to North Germanic cultures and requires the Northern Lords DLC. The Casus Belli can be used multiple times but each use will cost 1000 more Prestige than the previous one. It cannot be used by Kings or Emperors.

If the war ends in white peace the defender keeps his or her titles and if it ends in surrender it must also pay Gold and Prestige to the attacker. If the war ends by enforcing demands however it will have the following effects:

All titles held by the attacker are destroyed or given to other characters
All vassals are given independence
Attacker gains the War Target title and all titles that are de jure part of it
Attacker gains the Adventurer trait
Attacker gains 200 Gold
If the War Target title was a County and its de jure Duchy does not exist or is part of the defender's realm the Duchy is given to the attacker

When the Casus Belli is used for the first time it will spawn the following for the duration of the war the following army based on the number of owned Counties of the same Faith and Culture in the region of Mainland Scandinavia:

Counties	Levies	Varangian Veterans	Bondi	Vigmen	Huscarls
1	100	100	0	0	0
2	100	300	0	0	0
3	100	300	200	0	0
4	100	300	400	0	0
5	100	300	400	200	0
6	100	300	400	400	0
7	100	300	400	600	0
8	100	300	400	800	0
9	100	300	400	800	200
10	100	300	400	800	400

In addition if the character's Dynasty unlocked the first Adventure Dynasty Legacy it will gain an additional 100 Levies, 400 Varangian Veterans, 100 Bondi and 400 Vigmen.

AI Rulers will only use the Casus Belli if all their held titles are located in the Mainland Scandinavia region. If the Scandinavian Adventurers game rule is not set to Apocalyptic then they also require the Ambitious trait, as well as at least two of the following traits: Adventurer, Arrogant, Brave, Greedy.